Springs:
Springs are old and well known in the art. Generally speaking, a spring is an elastic object used to store mechanical energy. When compressed or stretched, depending on its design, a spring exerts a force proportional to its change in length (Hooke's law). This property is useful in countless applications and as such springs have been adopted for use in endless array of mechanical devices.
Various spring designs have been developed which are particularly well suited for specific applications. Some of these designs, which are of importance to this invention, are as follows.
Ribbon Springs:
The term ribbon spring is used to describe any number of spring designs having a rolled ribbon of flat or curved spring steel which produce a force when actuated out of their static curvature. Types of ribbon springs include the following:
Constant Force Springs (Conforce Springs):
A constant-force spring is a spring for which the force it exerts over its range of motion or length is a constant, or generally constant. That is, constant force springs do not obey Hooke's law. Generally speaking constant-force springs are constructed as a rolled ribbon of spring steel such that the spring is relaxed when it is fully rolled up, either around itself or around a spool. As it is unrolled, the restoring force comes primarily from the portion of the ribbon near the roll. Because the geometry of that region remains nearly constant as the spring unrolls, the resulting force is nearly constant.
More specifically, constant force spring includes a pre-stressed flat strip of spring material which is formed into virtually constant radius coils around itself or a spool. When the strip is extended (deflected) the inherent stress in the strip resists the loading force, the same as a common extension spring, but at a nearly constant (zero) rate. A constant torque is obtained when the outer end of the spring is attached to another spool and caused to wind in either the reverse or same direction as it is originally wound.
The full rated load of the spring is reached after being deflected to a length equal to 1.25 times its diameter. Thereafter, it maintains a relatively constant force regardless of extension length. Load is basically determined by the thickness and width of the material and the diameter of the coil.
Fatigue life ranges from 2,500 cycles to over a million cycles depending upon the load and size of the spring. Working deflections of 50 times the spool diameter can be achieved.
Constant force springs have been adopted for use in counterbalances, door closers, cable retractors, hose retrievers, tool head returns, cabinet & furniture components, gym equipment, hair dryers, toys, electric motors, appliances, space vehicles, and other long-motion functions. Constant force springs are particularly well suited in applications where a constant load is applied.
Variable Force Springs:
Variable force springs are similar to constant force springs in that they are constructed of a rolled ribbon of spring steel such that the spring is relaxed when it is fully rolled up. Variable force springs differ from constant force springs in that the force they produce intentionally varies along the length of the ribbon of spring steel. This varying force is accomplished by forming the pre-stressed flat strip of spring material into non-constant radius coils that wrap around itself or a spool. That is, the radius of the coils of the strip of spring material varies along the length of the strip of spring material. When the strip is extended (deflected) the inherent stress in the strip resists the loading force, the same as a common extension spring, but at a varying rate depending on the position of the deflection in the strip of spring material.
In some applications, it is desirable for the spring to have less force as it is extended, while in others it is preferable to have more force; in yet other applications it is desirable for the spring to have variable force along its length, that is as the spring is extended the force increases, then begins to decrease, then begins to increase again, then begins to decrease again and so on. A spring that produces less force while being extended is said to have a negative gradient. Negative gradients of as much as 25% or more are possible. A spring that produces more force as it is extended has a positive gradient. Positive gradients of 500% or more are possible.
Constant Torque Springs (Contorque Springs):
Constant-torque springs are similar to constant force springs and variable force springs in that they are constructed of a rolled ribbon of spring steel such that the spring is relaxed when it is fully rolled up. Constant torque springs differ from constant force springs and variable force springs in that a constant torque spring is made up of a specially stressed constant force spring traveling between two spools, a storage spool and an output spool. The spring is stored on the storage spool and wound reverse to its natural curvature on an output spool. When released, torque is obtained from the output spool as the spring returns to its natural curvature on the storage spool. No useful torque may be obtained from the storage spool. The torque produced by a constant torque spring can be constant over the entire retraction of the spring—known as constant force constant torque springs. The springs may also be designed to produce a negative gradient, or a positive gradient, in the manner described with respect to variable force springs—known as variable force constant torque springs. These unique features make this spring-form desirable for many applications, including counterbalances, clock motors, self-energizing position indicators, cord or cable retractors, and mechanical drives.
Architectural Coverings:
Architectural coverings are also old and well known in the art. The term architectural covering(s) is used herein to describe any architectural covering such as a blind, shade, drapery or the like, and the term is not meant to be limiting.
One common problem with many architectural coverings is that they have a torque profile that is not constant. That is, in a conventional architectural covering, which extends between an open position, wherein the shade material and bottom bar are adjacent one another near the top of a window in a fully collapsed position, and a closed position wherein the header and bottom bar are spaced as far away from one another as the shade material will allow in a fully extended position, the most amount of force is on the suspension cords in the open position whereas the least amount of force is on the suspension cords in the closed position. This is because the entire weight of the bottom bar and shade material is supported by the suspension cords in the open position, as well as some force for compressing the shade material. As the architectural covering is opened, because the shade material is connected to the header, more and more weight is transferred to the header (by the fact that the shade material is hanging from the header) and less and less weight is supported by the suspension cords. This varying weight profile provides a complex problem when trying to counterbalance and motorize an architectural covering.
Thus, it is a primary object of the invention to provide a system and method of manual and motorized manipulation of an architectural covering that improves upon the state of the art.
Another object of the invention is to provide a system and method of manual and motorized manipulation of an architectural covering that is easy to use.
Yet another object of the invention is to provide a system and method of manual and motorized manipulation of an architectural covering that is efficient.
Another object of the invention is to provide a system and method of manual and motorized manipulation of an architectural covering that is simple.
Yet another object of the invention is to provide a system and method of manual and motorized manipulation of an architectural covering that is inexpensive.
Another object of the invention is to provide a system and method of manual and motorized manipulation of an architectural covering that has a minimum number of parts.
Yet another object of the invention is to provide a system and method of manual and motorized manipulation of an architectural covering that has an intuitive design.
Another object of the invention is to provide a system and method of manual and motorized manipulation of an architectural covering wherein the counterbalance torque profile closely matches and varies along the length between an open position and a closed position of the architectural covering.
Yet another object of the invention is to provide a system and method of manual and motorized manipulation of an architectural covering that requires a minimal amount of power to open and close the architectural covering.
Another object of the invention is to provide a system and method of manual and motorized manipulation of an architectural covering that provides long battery life because a minimal amount of power is required to open and close the architectural covering.
Yet another object of the invention is to provide a system and method of manual and motorized manipulation of an architectural covering that allows for manual as well as motorized movement of the architectural covering.
These and other objects, features, or advantages of the present invention will become apparent from the specification and claims.